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Salmonella Infections an update

Salmonella Infections an update

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Salmonella Infections an update

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  1. SalmonellaInfections an update Dr.T.V.Rao MD Dr.T.V.Rao MD

  2. Salmonella • Causes Infections in Humans and vertebrates, • Enteric Fever ( Typhoid fever ) • Gastroenteritis • Septicemias, • Carrier state a concern Dr.T.V.Rao MD

  3. Salmonella • A Very complex group • Contains more > 2,000 spp • Typed on the basis of Serotyping, and species typing • Divided into two groups 1 Enteric fever group 2 Food poisoning group – Septicemias. Dr.T.V.Rao MD

  4. Key points • There are more than 2000 different antigenic types of Salmonella; those pathogenic to man are serotypes of S. enterica. • Most serotypes of S. enterica cause food-borne gastroenteritis and have animal reservoirs. • S. enterica serotypes Typhi and Paratyphi cause typhoid fever. Dr.T.V.Rao MD

  5. Enteric FeverTyphoid Fever • Caused by Salmonella typhi, and other Groups called as Paratyphoid A, B, C • Salmonella typhi - Causes Typhoid • Salmonella Paratyphi A,B,C Causes Paratyphoid fevers. • Food Poison group • Spread from Animals – Humans • Causes Gastroenteritis – Septicemias, Localized Infection Dr.T.V.Rao MD

  6. Typhoid fevers are prevalent in many regions in the World

  7. Typhoid Mary Most Dangerous Woman in America Dr.T.V.Rao MD

  8. Typhoid Mary • A famous example is “Typhoid” Mary Mallon, who was a food handler responsible for infecting at least 78 people, killing 5. These highly infectious carriers pose a great risk to public health.

  9. Typhoid Mary • "Typhoid Mary," real name Mary Mallon, worked as a cook in New York City in the early 1900s. Public health pioneer Sara Josephine Baker, MD, PhD tracked her down after discovering that she was the common link among many people who had become ill from typhoid fever She was traced to typhoid outbreaks a second time so she was put in prison again where she lived until she died.

  10. Morphology of Salmonella • Gram negative bacilli • 1-3 / 0.5 microns, • Motile by peritrichous flagella Dr.T.V.Rao MD

  11. S.typhi with Flagella Dr.T.V.Rao MD

  12. Bacteriology –Typhoid fever • The Genus Salmonella belong to Enterobacteriaceae • Facultative anaerobe • Gram negative bacilli • Distinguished from other bacteria by Biochemical and antigen structure Dr.T.V.Rao MD

  13. Different types of Salmonella I - entericaII - salamaeIIIa -arizonaeIIIb -diarizonaeIV - houtenaeV - bongoriVI - indica

  14. Cultural Characters • Aerobic / Facultatively anaerobic • Grows on simple media – Nutrient agar, • Temp 15 – 41ºc / 37º c • Colonies appear as large 2 -3 mm, circular, low convex, • On MacConkey medium appear Colorless ( NLF ) Selective Medium - Wilson Blair Bismuth sulphide medium. Produce Jet black colonies H2 S produced by Salmonella typhi Dr.T.V.Rao MD

  15. Enrichment MediumLiquid Medium • Selenite F medium • Tetrathionate broth • Above medium are used for isolation of Salmonella from contaminated specimens • Particularly stool specimens.. Dr.T.V.Rao MD

  16. Identifying Enteric Organisms • Isolates which are Non lactose fermenting • Motile, Indole positive • Urease negative • Ferment Glucose,Mannitol,Maltose • Do not ferment Lactose, Sucrose • Typhoid bacilli are anaerogenic • Some of the Paratyphoid form acid and gas • Further identification done by slide agglutination tests Dr.T.V.Rao MD

  17. Biochemical Characters • Glucose ,Mannitol ,Maltose produce A/G • Salmonella typhi do not produce gas • Lactose/Salicin/sucrose not fermented. • Indole – • Methyl Red + • V P - • Citrate + • Urea – • H2S – produced by Salmonella typhi • Paratyphi A do not produce H2S Dr.T.V.Rao MD

  18. Resistance of Salmonella • 55º c – 1 hour • 60º c – 15 MT • Boiling ,Chlorination, Pasteurization Destroy the Bacilli. Dr.T.V.Rao MD

  19. Antigenic structure of Salmonella • Two sets of antigens • Detection by serotyping • 1Somatic or 0 Antigens contain long chain polysaccharides ( LPS ) comprises of heat stable polysaccharide commonly. • 2 Flagellar or H Antigens are strongly immunogenic and induces antibody formation rapidly and in high titers following infection or immunization. The flagellar antigen is of a dual nature, occurring in one of the two phases. Dr.T.V.Rao MD

  20. SalmonellaAntigenic Structure • H – Flagellar antigens • O – Somatic antigen, • Vi – Surface antigen in some species only • H antigens also called flagellar antigens, heat labile protein, • Boiling destroys antigenicity • When mixed with Antiserum produces agglutination and fluffy clumps are produced • H antigens are strongly immunogenic Induces antibodies rapidly, Dr.T.V.Rao MD

  21. O Antigens Forms integral part of Cell wall, Like Endotoxin 0 Antigens unaffected by boiling. When mixed with antiserum produce chalky clumps are formed, take more time reaction, at high temp 50º – 55º c O antigens are less immunogenic. than H antigens Antigens – Salmonella ( cont ) Dr.T.V.Rao MD

  22. Antigen (Vi) – Salmonella ( contd ) • Vi antigens • Many strains in S.typhi covers the O antigens- prevents agglutination. • Resembles like K antigens • Destroyed after boiling at 60º c / 1 hour. • Vi a polysaccharide • Acts as virulence factor, protects the bacilli against Phagocytosis and activity of Complement • Poorly immunogenic • Low titer of antibodies are produced, Not diagnostic Dr.T.V.Rao MD

  23. Classification of Salmonella • Classified on the basis of Kauffmann-White Scheme • Structure of 0 and H antigens are taken into consideration, • More than 2000 species characterized. Dr.T.V.Rao MD

  24. Kauffmann – White scheme • Serotype 0 antigens H antigens Phase 1 2 1.Typhi 9,12,(Vi) d 1,2 2 Paratyphi A 1,2.12 a - 3 Paratyphi B 1,4,5,12 b 1,2 4 Typhimuruim 1,4,5,12 I 1,7 5 Enteritidis 1,9,12 g m 1,2 Dr.T.V.Rao MD

  25. Antigenic Variation in Salmonella • May be phenotypic / Genotypic • H to O = loss of Flagella May be phase variation from I to II V to W variation S to R variation Dr.T.V.Rao MD

  26. Pathogenicity • Salmonella are definite parasites to humans. • Eg S.typhi. • S.paratyphi A, B ,C • Other groups Salmonella • The important clinical syndromes 1. Enteric fever, Septicemias, gastroenteritis. Dr.T.V.Rao MD

  27. Enteric Fever: S. typhi • Ileocecal penetration • intraluminal multiplication • mononuclear response (macrophages) • Salmonella remains alive • 2nd week - lymphoid hyperplasia (mesenteric lymph nodes) • back to bowel

  28. Enteric FeverTyphoid • Typhoid – caused by S.typhi • Paratyphoid Caused by Paratyphi A,B,C • Typhoid --- Like Typhus • Infective dose ID50 / 107, Dr.T.V.Rao MD

  29. Fever • All the events coincides with Fever and other signs of clinical illness • From Gall bladder further invasion occurs in intestines • Involvement of peyr’s patches, gut lymphoid tissue • Lead to inflammatory reaction, and infiltration with monocular cells • Leads to Necrosis, Sloughing and formation of chacterstic typhoid ulcers

  30. Rashes in Typhoid • May present with rash, rose spots 2 -4 mm in diameter raised discrete irregular blanching pink maculae's found in front of chest • Appear in crops of upto a dozen at a time • Fade after 3 – 4 days

  31. Dr.T.V.Rao MD

  32. Events in a Typical typhoid Fever Dr.T.V.Rao MD

  33. Pathology and Pathogenesis • Bacilli enter through ingestion, • Bacilli attach to Microvilli,ileal mucosa, penetrate to Lamina propria and sub mucosa • Phagocytosis by Polymorphs and Macrophages • Enters the mesenteric lymph nodes • Enter the thoracic duct – Blood stream Dr.T.V.Rao MD

  34. Infective Dose • For human infections, the number of bacteria that must be swallowed in order to cause infection is uncertain and varies with the serotype. In most of these the median infective dose for most serotypes, including Typhi, has varied from 106 to 109 viable organisms. However, investigation of outbreaks suggests that in natural infection the infective dose might be fewer than 1000 viable organisms. Dr.T.V.Rao MD

  35. Pathology and Pathogenesis • Bacteremia Spread to Liver, Gall bladder, Spleen, Bone marrow, Lymph nodes, Lungs, Multiply in kidneys Once again spill into Blood stream Causes clinical illness. Dr.T.V.Rao MD

  36. Pathology and Pathogenesis • Multiply abundantly in Gall bladder, • Bile rich source of Bacteria • Spill into Intestine, infects payers patches, Lymph follicles • Inflammation – Undergo necrosis, Slough off • Typhoid ulcers • Typhoid ulcers can cause perforation and hemorrhage • Duration of Illness 3 – 4 weeks • Incubation 7 -14, ( 3-56 days ) Dr.T.V.Rao MD

  37. What is Enteric Fever Typhoid Fever • Enteric fever is caused by strains of S. Typhi or S. Paratyphi A, B or C; although S. Paratyphi B, which gene sequence analysis suggests is a variant of S. Java, is more likely to cause non-typhoidal diarrhoea. The clinical features tend to be more severe with S. Typhi (typhoid fever). After penetration of the ileal mucosa the organisms pass via the lymphatic's to the mesenteric lymph nodes, whence after a period of multiplication they invade the bloodstream via the thoracic duct. Dr.T.V.Rao MD

  38. Progress in Enteric Fever • The liver, gall bladder, spleen, kidney and bone marrow become infected during this primary bacteraemic phase in the first 7-10 days of the incubation period. After multiplication in these organs, bacilli pass into the blood, causing a second and heavier bacteraemia, the onset of which approximately coincides with that of fever and other signs of clinical illness. Dr.T.V.Rao MD

  39. Progress in Enteric Fever • From the gall bladder, a further invasion of the intestine results. Peyer's patches and other gut lymphoid tissues become involved in an inflammatory reaction, and infiltration with mononuclear cells, followed by necrosis, sloughing and the formation of characteristic typhoid ulcers occurs. Dr.T.V.Rao MD

  40. Immunity in Typhoid • Typhoid bacilli are Intracellular pathogens • Cell mediated immunity is crucial Dr.T.V.Rao MD

  41. Symptoms of Salmonellosis • Diarrhea • Nausea • Vomiting • Stomach pain • Headache • Fever • Onset 12-72 hours after infection

  42. Clinical manifestation • Head ache, malise,anorexia ,coated tongue • Abdominal discomfort, • Constipation / Diarrhea • Step ladder type fever, • Relative bradycardia, • A soft palpable spleen • Hepatomegaly • Rose spots appear Dr.T.V.Rao MD

  43. Events in a Typical typhoid Fever Dr.T.V.Rao MD

  44. Complications of Enteric fever • Intestinal perforation, • Hemorrhage, • Circulatory collapse. • Bronchitis Bronchopneumonia, • Meningitis, • Cholecystitis, • Arthritis,Periostitis / Nephritis, • Osteomyletis, Dr.T.V.Rao MD

  45. Relapses in Typhoid Fever • Apparent recovery can be followed by relapse in 5-10% of untreated cases. Relapse is usually shorter and of milder character than the initial illness, but can be severe and may be fatal. Severe intestinal haemorrhage and intestinal perforation are serious complications that can occur at any stage of the illness. Dr.T.V.Rao MD

  46. Other complications • Causes relapses in particular to patients treated with chloramphenicol. • S.paratyphi produce septicemias. Dr.T.V.Rao MD

  47. Typhoid carriers • Salmonella enterica causes approximately 16 million cases of typhoid fever worldwide, killing around 500,000 per year. One in thirty of the survivors, however, become carriers. In carriers the bacteria remain hidden inside cells and the gall bladder, causing new infections as they are shed from an apparently healthy host.

  48. Carrier Stage in Typhoid Fever • Most people infected with salmonella continue to excrete the organism in their stools for days or weeks after complete clinical recovery, but eventual clearance of the bacteria from the body is usual. A few patients continue to excrete the salmonellae for prolonged periods. The term chronic carrier is reserved for those who excrete salmonellae for a year or more. Dr.T.V.Rao MD

  49. Carrier Stage in Typhoid Fever • Chronic carriage can follow symptomatic illness or may be the only manifestation of infection. It can occur with any serotype, but is a particularly important feature of enteric fever: up to 5% of convalescents from typhoid and a smaller number of those who have recovered from paratyphoid fever become chronic carriers, many for a lifetime. Dr.T.V.Rao MD

  50. Carrier Stage in Typhoid Fever • The bacilli are most commonly present in the gall bladder, less often in the urinary tract, and are shed in faeces and sometimes in urine. The long duration of the carrier state enables the enteric fever bacilli to survive in the community in non-epidemic times and to persist in small and relatively isolated communities. Dr.T.V.Rao MD